LONG Hood on an A Series 50mm f/1.4

**UncleVanya** · 10-09-2015, 02:28 PM

Originally posted by wkraus

Dark corners--unless I'm in for a surprise!
Do you own a film body?

I do - however this was intended as an observation of how the lens and hood performs on APSC. Also why would you expect dark corners at f/11? Vignetting is typically worst at wide open f stops.

stevebrot · 10-09-2015, 07:07 PM

Originally posted by UncleVanya

Also why would you expect dark corners at f/11? Vignetting is typically worst at wide open f stops.

That is the case for optical vignette generated by the lens. If you have too narrow a hood, it gets more distinct as you stop down.

Steve

**UncleVanya** · 10-09-2015, 07:29 PM

Originally posted by stevebrot

That is the case for optical vignette generated by the lens. If you have too narrow a hood, it gets more distinct as you stop down.

Steve

Neat. I will try it tomorrow.

wkraus · 10-10-2015, 12:09 AM - **1 Like**

Originally posted by UncleVanya

I do - however this was intended as an observation of how the lens and hood performs on APSC.

I'm asking because my method of determining if a hood does fit a specific lens involves a film body. I carried this method over from my film days. For full format, put the lens + hood combo on the camera, set the shutter to B, open or detach the back and open the shutter (works best with a camera that allows you to lock the shutter open). Now by looking at the film window corners through the lens against a uniform bright background you can see if the hood obstructs the light path. You can do this from both sides. From the back trying to bring the extreme corner in line with the barrel edge you can see the corners turn dark if the hood is too long. Depending on the focal length and construction it may be easier to see from the front. If you can see through the extreme corners until your view is covered by the barrel edge you're fine. If the hood covers the outer part of the view it is too long. This also works for the edges with rectangular or tulip-shaped hoods.

To do the same for my APS-C camera, I fixed a 35 mm wide strip of black paper with a 16 by 24 mm window in the middle of the film window (that's why I was asking for a film body) and proceeded the same way.

In my early film days I was using my M 1.4/50mm with the plastic hood for the M 85 and 100mm lenses because I could not see any vignetting. By this method I found out that there was some vignetting up to f/4 while smaller apertures were no longer obstructed by the hood. While the vignetting in that case is rather insignificant, in theory at least there may also be some diffraction involved with an effect on resolution.

I'm now using the FA 1.4/50mm and on APS-C the longest of my several hoods that does not vignette is, again, the plastic hood for the M 85 and 100mm lenses. The metal hood for the Takumar 105mm is too long.

kh1234567890 · 10-10-2015, 01:05 AM

Originally posted by UncleVanya

For grins I decided to mount my SMC A series 50mm f/1.4 on the K3 and have a little fun. I wanted to see how long a hood was too long. I had a couple of hood lying around and thought I would try them out. I started with the longest 49mm native threaded hood I had - a genuine Pentax metal hood designed to fit the Takumar 135mm f/3.5 and the f/5.6 200mm lenses. The hood is at least as long as the lens which makes it look quite funny mounted there but what the heck.

You could always try a really short hood

https://www.pentaxforums.com/forums/22-pentax-camera-field-accessories/218605...ood-shape.html
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/219144-pent...pness-fix.html

**UncleVanya** · 10-10-2015, 05:47 AM

Just beware that some of the step down ring hoods mentioned actually change the maximum aperture. The 50mm 1.4 for example with a 28mm step down ring should become a 1.8 or so. The D FA 100 with the same ring becomes f3.5, at least that's what my math indicated ( Focal length ÷ opening diameter)

Just be sure the diameter of the ring doesn't limit your lens f stop wide open. For the 50 f1.4 that's means a 36mm step down is as small as you should go if you want to use it wide open.

**UncleVanya** · 10-19-2015, 02:27 PM

Had time today to shoot a couple at f/11 on the F 50 f/1.7 - no time for the manual focus 1.4 yet at that f/stop.

---------- Post added 10-19-15 at 05:29 PM ----------

Originally posted by stevebrot

That is the case for optical vignette generated by the lens. If you have too narrow a hood, it gets more distinct as you stop down.

Steve

See attached pics. I don't see anything do you?
Admittedly this was with the F 50 f/1.7 not the A 50 f/1.4 so not definitive yet.

Attached Images

View Picture EXIF

View Picture EXIF

**UncleVanya** · 10-19-2015, 02:49 PM

Found the time for the A 50mm f/1.4 repeat test.

Two shots of blue sky at f/11 - one with the hood and one without. Also an f/2 shot - meant to do another f/1.4 but slipped up and didn't notice before the sky started to get too dark.

wkraus · 10-20-2015, 12:25 PM

Originally posted by UncleVanya

Found the time for the A 50mm f/1.4 repeat test.

Two shots of blue sky at f/11 - one with the hood and one without. Also an f/2 shot - meant to do another f/1.4 but slipped up and didn't notice before the sky started to get too dark.

Looks fine. The procedure I described above showed me that the 85-100 hood causes some vignetting with the FA 50/1.4 on FF at wider f-stops than f/4, but none with smaller ones. However, if you are fine with the results this is immaterial. Pronounced vignetting gets worse with smaller f-stops; minimal vignetting goes away as you stop down.

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10-09-2015, 02:28 PM	#16
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,403 Original Poster	Originally posted by wkraus Dark corners--unless I'm in for a surprise! Do you own a film body? I do - however this was intended as an observation of how the lens and hood performs on APSC. Also why would you expect dark corners at f/11? Vignetting is typically worst at wide open f stops.

10-09-2015, 07:07 PM	#17
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by UncleVanya Also why would you expect dark corners at f/11? Vignetting is typically worst at wide open f stops. That is the case for optical vignette generated by the lens. If you have too narrow a hood, it gets more distinct as you stop down. Steve

10-09-2015, 07:29 PM	#18
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,403 Original Poster	Originally posted by stevebrot That is the case for optical vignette generated by the lens. If you have too narrow a hood, it gets more distinct as you stop down. Steve Neat. I will try it tomorrow.

10-10-2015, 12:09 AM - 1 Like	#19
wkraus Pentaxian Join Date: Jan 2013 Location: Near Vienna, Austria Photos: Gallery Posts: 2,060	Originally posted by UncleVanya I do - however this was intended as an observation of how the lens and hood performs on APSC. I'm asking because my method of determining if a hood does fit a specific lens involves a film body. I carried this method over from my film days. For full format, put the lens + hood combo on the camera, set the shutter to B, open or detach the back and open the shutter (works best with a camera that allows you to lock the shutter open). Now by looking at the film window corners through the lens against a uniform bright background you can see if the hood obstructs the light path. You can do this from both sides. From the back trying to bring the extreme corner in line with the barrel edge you can see the corners turn dark if the hood is too long. Depending on the focal length and construction it may be easier to see from the front. If you can see through the extreme corners until your view is covered by the barrel edge you're fine. If the hood covers the outer part of the view it is too long. This also works for the edges with rectangular or tulip-shaped hoods. To do the same for my APS-C camera, I fixed a 35 mm wide strip of black paper with a 16 by 24 mm window in the middle of the film window (that's why I was asking for a film body) and proceeded the same way. In my early film days I was using my M 1.4/50mm with the plastic hood for the M 85 and 100mm lenses because I could not see any vignetting. By this method I found out that there was some vignetting up to f/4 while smaller apertures were no longer obstructed by the hood. While the vignetting in that case is rather insignificant, in theory at least there may also be some diffraction involved with an effect on resolution. I'm now using the FA 1.4/50mm and on APS-C the longest of my several hoods that does not vignette is, again, the plastic hood for the M 85 and 100mm lenses. The metal hood for the Takumar 105mm is too long.

10-10-2015, 01:05 AM	#20
kh1234567890 Veteran Member Join Date: Sep 2010 Location: Manchester, UK Photos: Gallery Posts: 2,653	Originally posted by UncleVanya For grins I decided to mount my SMC A series 50mm f/1.4 on the K3 and have a little fun. I wanted to see how long a hood was too long. I had a couple of hood lying around and thought I would try them out. I started with the longest 49mm native threaded hood I had - a genuine Pentax metal hood designed to fit the Takumar 135mm f/3.5 and the f/5.6 200mm lenses. The hood is at least as long as the lens which makes it look quite funny mounted there but what the heck. You could always try a really short hood https://www.pentaxforums.com/forums/22-pentax-camera-field-accessories/218605...ood-shape.html https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/219144-pent...pness-fix.html

10-10-2015, 05:47 AM	#21
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,403 Original Poster	Just beware that some of the step down ring hoods mentioned actually change the maximum aperture. The 50mm 1.4 for example with a 28mm step down ring should become a 1.8 or so. The D FA 100 with the same ring becomes f3.5, at least that's what my math indicated ( Focal length ÷ opening diameter) Just be sure the diameter of the ring doesn't limit your lens f stop wide open. For the 50 f1.4 that's means a 36mm step down is as small as you should go if you want to use it wide open.

10-20-2015, 12:25 PM	#24
wkraus Pentaxian Join Date: Jan 2013 Location: Near Vienna, Austria Photos: Gallery Posts: 2,060	Originally posted by UncleVanya Found the time for the A 50mm f/1.4 repeat test. Two shots of blue sky at f/11 - one with the hood and one without. Also an f/2 shot - meant to do another f/1.4 but slipped up and didn't notice before the sky started to get too dark. Looks fine. The procedure I described above showed me that the 85-100 hood causes some vignetting with the FA 50/1.4 on FF at wider f-stops than f/4, but none with smaller ones. However, if you are fine with the results this is immaterial. Pronounced vignetting gets worse with smaller f-stops; minimal vignetting goes away as you stop down.